Amateur ExtraE7C04
How does an impedance-matching circuit transform a complex impedance to a resistive impedance?
C
Answer
Practical circuits and system design
Type
A
It introduces negative resistance to cancel the resistive part of impedance
B
It introduces transconductance to cancel the reactive part of impedance
C
It cancels the reactive part of the impedance and changes the resistive part to the desired value
D
Reactive currents are dissipated in matched resistances
Answer Notes
A complex impedance consists of both a resistive (real) and a reactive (imaginary) component. To achieve a purely resistive match, an impedance-matching circuit must introduce a reactance that is equal and opposite to the load's reactance, effectively canceling it out.
Once the reactive part is neutralized, the matching circuit acts like a transformer to adjust the remaining resistive component up or down to match the desired system impedance, which is typically 50 ohms.
Distractors mentioning 'negative resistance' or 'transconductance' are incorrect because they refer to active device properties, not passive matching networks. Furthermore, reactive power is not 'dissipated' as heat; it is simply canceled by opposing reactances.
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